Most circuit structures of the traditional converters for a solar power generation or photovoltaic system are configured in single or two stages of circuit to connect with the public electrical supplies in parallel. The power regulators of household photovoltaic systems are generally built by assembling photovoltaic modules in parallel and/or in series to provide high DC-voltage power. If one of the photovoltaic modules, however, does not work, the output power and performance of the overall system may then decline considerably. Therefore, the integration of a DC-to-AC power inverter with a single photovoltaic module has been developed recently. Through the DC-to-AC power inverter, low-voltage DC power of a photovoltaic module can be converted into AC power to be connected with the public electrical supplies in parallel, with higher operational efficiency and systematic reliability. Moreover, due to the resultant power of low capacity, the distribution system can be constructed with cost advantages of low-capacity specification and low loss of transmission.
Conventional inverters are configured in the two-stage switching mode, in which the switching frequencies are usually about tens of KHz; this leads to a larger volume of the transformer or the inductor in the resonant circuit. Meanwhile, more than two current sensing devices are necessary in the two-stage mode to respectively control the AC output power and the DC input power. It is in need of a control strategy for the switching mode to achieve a DC-to-AC power inverter of competency for photovoltaic modules.